Dispersing powder and process of making



Patented Apr. 10, 1928.

UNITED STATES PATENT OFFICE.

EDWARD R. ALLEN AND WILFORD E. KAUTMANN, E EAST ORANGE, NEW JERSEY,

-ASSIGNORS TO E. I. DU PON'I. DE NEMOURS &, COMPANY, OF WILMINGTON, DELA- WARE, A CORPORATION OF DELAWARE.

DISPERSING POWDER AND PROCESS OF MAKING.

Io Drawing.

This invention relates to the production of quickly wetting and dispersing powders of the ordinary pigments, which powders are adapted to be used in the art of glazing and coating paper and in the wall paper industries, as well as in the preparation of socalled water colors in general. :These powders as prepared by us possess the novel and surprising property of mixing readily in water. By reason of this property, the new. powders" give satisfactory results in many types of industrial operations, in which the use of powders prior to our invention has been impractical orimpossible, since, when the ordinary dried powders were used they would not disperse appreciably or even wet up readily in water, and would consequently produce streaked and uneven effects on the goods. Full or satisfactory tinctorial value was by no means obtained from the'pigment in such powders, and it was necessary to employ-instead pulps, that is, pigments in the form of pastes or wet cakes.

The use of pulps also, however, entails several disadvantages, among them being the danger of their freezing in cold weather, the necessity of transporting them "in waterproof containers, and their bulk and excessive weight due to their water content which renders them inconvenient to handle and expensive to ship. \Vith this state of the art in mind we have succeededin producing dry powders which have none of the objection-- able features of a paste, and have also developed a method for their manufacture. These powders when mixed thoroughly with water, disperse in an entirely satisfactory manner.

This result we accomplish by the very thorough incorporation into the original pulp of suitable colloidal substances, either water-absorbing or true dispersing agents, which substances impart to the pigmentthe 4 property of wetting up in water after drying. This effect is produced to a certain extent with such substances as starches, .gums, and dextrines, but more effectively by the nse'of'true dispersing agents such as soaps, Turkey red oil, licorice, saponin, and soap bark extract of commerce, consisting largely of saponin.

In the manufacture of our powders any of Application filed July 3, 1925. Serial No. 41,432.

the ordinary water insoluble pigments generally employedin the preparation of water colors as lead chromate, lead sulphate, lead phosphate, Prussian blue, etc., may be employed. In general, the pigment in the form .of the original pulp or wet cake is mixed w1th the same amountor more of water to form a paste, and is worked up with the dispersing agent by stirring or vigorous agitation until the latter is thoroughly incorporated therewith. With continued agitation the paste is converted into a smooth foamy mass of increased volume, the amount of increase depending upon the particular dispersing agent-and the amount thereof employed. In general, the dispersing agent is added in such quantities as to approximate from 1% to 10% of the weight of the dry pigment. The smooth foamy mass resulting from the use of saponin, licorice, soap bark extracts and soap may approximate from two to three times the volume of the original charge. This mass is now dried. Such drying may be affected in any ordinary manner without regard to a particular apparatus; as by a current of warm air, on the surface of a heated drum, in a belt drier or by any other appropriate method. The dried mass is now ground to a powder which is the final product.

The following specific examples will serve to illustrate our process as applied to several representative pigments, it being understood that we do not confine ourselves to the .'proportions or materials hereinafter mentioned Ewample 1. Production of w dis ersing powder of a chrome yellow.

A smooth paste (consisting of 50-85% water) of the ordinary pigment known in the trade as lemon yellow, and consisting of a mixture of lead chromate, lead sulphate and lead phosphate, is stirred up in the resence of saponin equal to 1 to 10% o the weight of dry pigment present. In a short time a smooth foam results which is 2 to 3 times the volume of the original charge. This foam when dried grinds to a. powder which shows considerable dispersion when thrown directly into water, and when stirred up ,for some hours .with an equal weight of wa'ter, gives a smooth foaming 'pulp' which disperses equally as well in'a large volume of water as does the original undried pulp.

Example 2. Production of a dispersing powder of a chrome yellow. The rocedure is exactly the same as in Example 1, except that a solution of licorice is used in place of the saponin. Slightly less foaming results in connection with this dis persing agent-{yet the results from a practical standpoint are essentially the same.

E'zvample 3. Prodzwtion of a dispersing powder of'a chrome green.

' A smooth paste (30 to 50% solids) is made of a chrome n pi ent consistin of 29.73% of lea chromate and 3.26% russian blue. To this is added a 50% solution of Turkey red oil (ammonium salt of sulphonated castor oil) in an amount equal to 10% of the weight of the dry content of the 10% of the solids o aste and the mixture, agitated for some ours. The alkalinity of the charge is then carefully neutralized with a watery extract of casein (obtained by boiling up commercial casein -with water), stirred an hour or more longer then dried and ground. This product when stirred up' with water for some ours or preferably mechanically agitated.

over night, forms a smooth pulp which disperses in water in a manner comparable to the original pulp.

Example 4. Product of adispersirg powder of a chrome green.

- A smooth paste (20 to solids) of a chrome green, medium shade, consisting of 29.73% lead chromate, and 3.26% Prussian blue is stirred up in the-presence of soap bark extract containin solids equal to 1 to the pigment paste. With vigorous agitation the paste approxi: mately triples in volume as was true in the case cited under Example 1. The foamy product when dried and ground disperses appreciably when introduced into water,

but to an extent equal to the original pulp if stirred up with water under the conditions described in Example 1.

'5. of a dispersing powder of Pmsz'an blue.

A pai'ste of Prussian blue (approximately water) is stirred up with good agitation and partially dispersed with sodium or potassium oxalate, (the dispersing action of oxalates on Prussian blue' is well known, Bancroft, Applied Colloid Chemistry p.

' 177), equal in weight to 2% of the solid content of the pigment paste. Soap bark extract containing solids equal to 1 to 10% the total solids content of the pigment is then added and the whole stirred thoroughly until t good foam structure is produced. During this agitationv it is necessary to add water gradualy so that the final foam is about 85% water. This product when dried and ground will give when stirred up with water under the conditions described under Example 1'a smooth pulp which will disperse in water equally as well as the original undried pulp.

It will be understood that by the term a of their influence on surface tension where by they are thought to distribute themselves in infinitesimal films over the surfaces of the particles.

. We claim:

1. The process of preparing a dry water I dispersible powder from an inorganic 'pigment notreadily miscible with water which comprises agitating an aqueous mixture containing said pigment and an amount of a dispersing agent between 1% and 10%, by weight of the pigment, to produce a homogeneous mass, drying said mass and grinding it to a colloid like condition.

2. A process for preparing a dry water dispersible powder from a water insoluble pigment, which comprises agitating said pigment with water and a dispersing agent until the agent is thoroughlyincorporated, slowly adding water durlng such agitation .to produce a mass of foam comprising about 85% water, drying the resulting mass and grinding the dried mam to a powder.

3. A process for preparing a dry water dispersible powder from a water insoluble inorganic pigment which'comprises mixing a dispersing agent with an aqueous paste of said pigment, said agent being added. in such quantity as not to exceed 10% by weight of the dry pigment, agitating to produce a homogeneous mass of foam, drying said mass and reducing the dried mass to a powder. I

4. In a process for preparing a dry water dispersible powder from an aqueous paste of a water insoluble inorganic pigment the steps of addingsaponin to said paste and thenconverting the paste to a mass of foam.

' 5. In a process for preparing a dry' water dispersible powder from an. aqueous paste of a water insoluble inorganic pigment the steps of converting said paste to' a mass of foam and drying said mass.

6. In a process for preparing a dry water dispersible powder from an aqueous paste of a water insoluble inorganic pigment the steps of converting said paste to a mass 'of foam, drying said mass and grinding the dried mass.

7. A process for preparing a dry water dispersible powder from a water insoluble inorganic pigment which comprises adding a foam producing dispersing agent to an aqueous paste of saidpigment, agitating until a mass of foam is formed, drying, and grinding the dried mass. 7

8. In a processfor preparing a dry water dispersible powder from an aqueous paste of a water insoluble inorganic pigment the steps 'of incorporating with said paste a foam producing dispersing agent and then agitating the mixture into a mass of foam.

9.A process for preparing a dry water dispersible powder from an aqueous paste of a water insoluble inorganic pigment which comprises adding a foam producing dispersing agent to said paste, agitating to produce a mass of foam and converting said mass to a powder.

10. A process for producing a water insoluble inorganic pigment in dry, water dising characterized by the property of dispersloid like powder obtained ing readily in water to form a smooth pulp. 12. A dry colloid like-powder obtained by agitating an aqueous mixture of an inor:

ganic pigment not readily miscible with water and an amount; of a foam producing dispersing agent between 1% and 10%, by

weight of said pigment until a homogeneous mass approximating from two to three times the volume of the original mixture results, drying said mass and grinding, said powder being characterized by'the property of dispersing readily in water to form a smooth pul 13. A water dispersible powder comprising a uniform mixture of a water insoluble inorganic pigment and a foam producing dispersing agent, said agent being present in an amount less than 10%, by weight, of the pigment. 1

14. A water dispersible powder comprising a uniform mixture of a water insoluble inorganic pigment andsaponin, said 'saponin being present in an amount lessthan 10%,

by Weight, of the pigment.

15. A dry colloid like powder obtained by agitating an aqueous mixture of an inorganic pigment not readily-miscible v with water and a foam producing dispersing agent until a mass of foam is produced, drying said mass and grinding, said powder persing readily in water to form a smooth p 'p-v 16. A water dispersible powder comprising an inorganicpigment, the particles of sad powder having the structure of ground dried-foam.

. In testimony whereof we aflix our signatures.

EDWARD R;- ALLEN. WILFORD E; KAUFMANN.

being characterized by the-property of dis- 

